1. Technical Field
The present invention relates to a method for analyzing a load characteristic of a cylindrical object to be analyzed and an analysis model creation apparatus.
2. Related Art
A vehicle is equipped with an energy absorbing member that, at the time of the occurrence of collision, is crushed and absorbs the collision energy. As a typical example of the energy absorbing member, a crash box disposed between a front bumper beam and a front frame is given. Conventionally, an energy absorbing member made of a metal material such as a steel sheet has been used; but these days, an energy absorbing member made of a fiber-reinforced resin in which carbon fibers are mixed (CFRP) is in practical use in order to reduce the weight of the car body.
Such an energy absorbing member made of a CFRP forms a cylindrical shape; and when a collision load is inputted in the axial direction, the energy absorbing member is crushed while being squashed continuously in an outward or inward winding manner. A crash box formed of a steel sheet is squashed while being buckled at relatively large intervals; on the other hand, the energy absorbing member made of a CFRP is continuously squashed, and therefore, also in terms of load characteristics, has the advantage that the crushing load is stable.
As a computer-aided engineering (CAE) technology that analyzes the load characteristic at the time of the axial crushing of such an energy absorbing member made of a CFRP, there is a method in which an analysis model of the energy absorbing member is constructed by a mesh pattern and an analysis is performed by the finite element method. The finite element method is a simulation method using a computer in which a structure body to be analyzed having infinite degrees of freedom is virtually divided into a finite number of mesh cells and the deformation of each mesh cell due to collision is analyzed by simulation. In general, the mesh cells used for the collision analysis by the finite element method are disposed in the axial direction, which is the direction in which a load is inputted, and the direction orthogonal to the axial direction (see, for example, Japanese Unexamined Patent Application Publication (JP-A) No. 2007-249643 and JP-A No. 2008-33689).
However, when an analysis is performed using a conventional mesh pattern, there is a case where a variation range of crushing load, which is originally supposed to transition stably, appears greatly and the degree of reproducibility of the analysis result with respect to the actual object to be analyzed is low. In particular, depending on the size of the mesh cell, there has been a case where spike peaks appear in the load characteristic at intervals corresponding to the length of one side of the mesh cell, and the variation of crushing load is further increased.